Dietary Modification of Serum Cholesterol in the Chick

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Abstract
Chicks were fed herring oil, corn oil, Crisco, lard, butter and chicken fat in diets containing 20 and 26% of protein. The chicks fed the higher protein level showed lower serum cholesterol levels than those fed the lower protein level whether or not the diet was supplemented with fat and regardless of the type of fat added to the diet. With both protein levels Crisco, butter, lard and chicken fat increased serum cholesterol. Herring oil did not increase serum cholesterol with either diet and corn oil did so to a significant degree only in the case of the chicks fed the 20% protein diet. When the chicks were 5 weeks old, 1% of cholesterol was fed in the respective diets for 48 hours. Serum cholesterol was markedly increased by the treatment in every instance with the chicks receiving supplementary fat showing higher cholesterol values than the chicks fed the diets without added fat. Butter and lard resulted in the least increase over the control diet with the chicks on the 20% protein diet, but the greatest increase with the chicks on the 26% protein diet. The differences in the effects of the various fats, depending upon the protein content of the diet are considered to result from increased absorption of the fats and cholesterol from the intestine in the chicks fed the higher level of protein. The weights of the thyroid glands of chicks fed the various diets (without added cholesterol) were determined. There was a negative correlation between thyroid size and serum cholesterol level. Relative to body weight the thyroid glands were lighter in the chicks fed the lower level of protein. The data suggest that the effect of diet upon serum cholesterol level may be mediated to some extent through the thyroid gland.